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19 Cards in this Set

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An object goes from one point in space to another. After it
arrives at its destination, its displacement is:
1. either greater than or equal to
2. always equal to
3. either less than or equal to
4. not related to
the distance it traveled.
3. either less than or equal to
Displacement can be negative, and when it is, it is less than
distance, which is the absolute value of displacement!
A skydiver is falling straight down, along the negative
y direction. During the initial part of the fall, her speed
increases from 16 to 28 m/s in 1.5 s. What sign are
the velocity and acceleration?
v<0, a<0
During a later part of the fall, after the parachute has
opened, her speed decreases from 48 to 26 m/s in 11 s.
Which of the following is correct?
1) v>0, a>0
2) v>0, a<0
3) v<0, a>0
4) v<0, a<0
3) v<0, a>0
If speed is increasing, v and a are in same direction.
If speed is decreasing, v and a are in opposite direction.
A ball is thrown straight up in the air and returns to its initial position.
For the time the ball is in the air, which of the following statements is
true?
1 - Both average acceleration and average velocity are zero.
2 - Average acceleration is zero but average velocity is not zero.
3 - Average velocity is zero but average acceleration is not zero.
4 - Neither average acceleration nor average velocity are zero.
3 - Average velocity is zero but average acceleration is not zero.
Free fall: acceleration is constant (-g)
Initial position = final position: Δx=0
⇒ ave vel = Δx/ Δt = 0
An object is dropped from rest. If it falls a distance D in time t
then how far will if fall in a time 2t ?
1. D/4
2. D/2
3. D
4. 2D
5. 4D
4. 2D
Correct x=1/2 at2
An object is dropped from rest. If the object has speed v at
time t then what is the speed at time 2t ?
1. v/4
2. v/2
3. v
4. 2v
5. 4v
4. 2v

Correct v=at
I am going to roll the ball down the inclined plane. If the ball
reaches mark at distance 1 ft at time t1, when will the ball reach
the mark at distance 9 ft?
1. t9 = 9t1
2. t9 = √18 t1
3. t9 = 3t1
3. t9 = 3t1
x=1/2VoT +1/2at2
A ball is thrown downward (not dropped) from the top of a
tower. After being released, its downward acceleration will
be:
1. greater than g
2. exactly g
3. smaller than g
2. exactly g
after the ball is released, it is only being accelerated by gravity, the throw just sets the initial velocity
A ball is thrown vertically upward. At the very top of its
trajectory, which of the following statements is true:
1. velocity is zero and acceleration is zero
2. velocity is not zero and acceleration is zero
3. velocity is zero and acceleration is not zero
4. velocity is not zero and acceleration is not zero
3. velocity is zero and acceleration is not zero
At the top of the path, the velocity of the ball is
zero,but the acceleration is not zero. The velocity at
the top is changing, and the acceleration is the rate at
which velocity changes.
Dennis and Carmen are standing on the edge of a
cliff. Dennis throws a basketball vertically upward,
and at the same time Carmen throws a basketball
vertically downward with the same initial speed.
You are standing below the cliff observing this
strange behavior. Whose ball is moving fastest
when it hits the ground?
same, when denis's ball returns to it's initial position it's velocity equals the initial velocity, the same as carmen's
Without air resistance, an object dropped from a plane
flying at constant speed in a straight line will
1. Quickly lag behind the plane.
2. Remain vertically under the plane.
3. Move ahead of the plane
2. Remain vertically under the plane.
There is no acceleration along
horizontal - object continues to
travel at constant speed (same as
that of the plane) along horizontal.
Due to gravitational acceleration
the object’s speed downwards
increases.
A seagull flies through the air with a velocity of 9 m/s if there
were no wind. However, it is making the same effort and flying
in a headwind. If it takes the bird 20 minutes to travel 6 km as
measured on the earth, what is the velocity of the wind?
1. 4 m/s
2. -4 m/s
3. 13 m/s
4. -13 m/s
2. -4 m/s
Seagull’s velocity relative to the wind = 9 m/s
• i. e., in the frame relative to the wind, wind velocity is zero
• Seagull travels at 6000/1200 = 5 m/s relative to earth. Therefore,
the wind velocity relative to earth is 5-9=-4 m/s.
A seagull is flying at 9m/s and covers 6.00km to an island and back.
How are the rounds-trip times with and without a 4.00m/s wind related
if the seagull always goes at 9.00 m/s relative to the wind?
1. The round-trip time is the same with/without the wind
2. The round trip time is always larger with the wind
3. It is not possible to calculate this
2. The round trip time is always larger with the wind
Time taken for the round trip without wind is: 12000 m / 9 m/s
= 1333 s = 22.2 minutes
• Time taken for the round trip with wind is: 27.7 minutes
Three swimmers can swim equally fast relative to the water. They have a race
to see who can swim across a river in the least time. Relative to the water,
Beth (B) swims perpendicular to the flow, Ann (A) swims upstream, and Carly
(C) swims downstream. Which swimmer wins the race?
A) Ann
B) Beth
C) Carly
beth
Beth will reach the shore first because the vertical component of
her velocity is greater than that of the other swimmers.
 The key here is how fast the vector in the vertical direction is. "B"
focuses all of its speed on the vertical vector, while the others
divert some of their speed to the horizontal vectors.
Time to get across =
width of river/vertical component of velocity
An object is held in place by friction on an inclined surface. The
angle of inclination is increased until the object starts moving. If
the surface is kept at this angle, the object
1. slows down
2. moves at uniform speed
3. speeds up
4. none of the above
3. speeds up
When the object is at rest net force on it is zero.
When the object starts to move there is change in velocity - i.e.,
there is acceleration or a net force due to gravity
The force remains constant when inclination is kept at that angle
leading to constant acceleration - continuous speed up.
You are a passenger in a car and are not wearing your seat belt.
Without increasing or decreasing its speed, the car makes a sharp
left turn, and you find yourself colliding with the right-hand side
door. Which of the following is correct analysis of the situation?
Before and after the collision there is a rightward force
pushing you into the door
Starting at the time of collision, the door exerts a leftward
force on you
Starting at the time of collision, the door exerts a leftward
force on you
Law of inertia: your body tends to move in a straight line forward.
It collides with the door which being part of the car is beginning to
curve leftward. When the contact happens you feel the door’s
force on you.
You are pushing a wooden crate across the floor at
constant speed. You decide to turn the crate on end,
reducing by half the surface area in contact with the
floor. In the new orientation, to push the same crate
across the same floor with the same speed, the force
that you apply must be about
a) four times as great
b) twice as great
c) equally as great
d) half as great
e) one-fourth as great
equally as great
as the force required before you changed the crate
Fricotrioiennalt faotricoen d.
oes not depend on the area of contact. It depends only on
the normal force and the coefficient of friction for the contact.
Consider a person standing in an elevator that is accelerating
upward. The upward normal force N exerted by the elevator floor
on the person is
a) larger than
b) identical to
c) less than
the downward weight W of the person.
a) larger than
Person is accelerating upwards - net upwards force is non zero
You are driving a car up a hill with constant velocity. On a piece of
paper, draw a Free Body Diagram (FBD) for the car.
How many forces are acting on the car? Name them
1
2
3
4
5
3
normal force, weight, road on car